// 引入 events 模块
var events = require('events');

var eventEmitter = new events.EventEmitter();


var connectHandler = function connected() {
   console.log('连接成功。');
   eventEmitter.emit('data_received');
}

eventEmitter.on('connection', connectHandler);

eventEmitter.on('data_received', function(){
   console.log('数据接收成功。');
});

eventEmitter.emit('connection');

console.log("程序执行完毕。");
